Huntington's Disease (HD) is a genetic disorder with clinical onset in middle adulthood, characterized by progressive mental and neurological impairment. We propose to survey 100 HD patients and 100 family members not at-risk for HD in order to assess the relative incidence of variants of plasma cholinesterase E1 and E2. Based on a recently reported British study of 28 patients, we anticipate finding an increased incidence of the rare E1 gene and the C5+ variant of cholinesterase in HD patients. The reported association between are cholinesterase variants and HD is unexplained; we hope to distinguish between modification of expression of the HD gene through the action of cholinesterase on the one hand and possible close linkage or allelism of the genes for cholinesterase and HD on the other. The derived data should offer promising clues to various research approaches concerning the prevention, prediction, diagnosis and treatment of HD.